2 Answers
2

Some parts of the image can’t currently be upgraded, so it is best to deploy a full updated image. Some individual apps can be updated with apt, though. First add the phablet-team ppa (https://launchpad.net/~phablet-team/+archive/ppa) to /etc/apt/sources.list. Then run the following command with root permissions to update apps:

# apt-get update && apt-get upgrade

This part is from the Ubuntu Touch release notes. In short, you can upgrade to the newest packages but sometimes when some of the Android stuff gets updated, you still need to reflash like you have been doing.

I guess you should be able to use adb pull/push to make a backup of /data/ubuntu/home/phablet
or rsync / scp (if you have openssh-server installed) to make a backup of /home/phablet
which you can restore after the upgrade.